1. Department of Hygiene and Epidemiology; University of Ioannina School of Medicine; Ioannina Greece
2. Julius Center for Health Sciences and Primary Care; University Medical Center Utrecht; Utrecht The Netherlands
3. The Dutch Cochrane Centre, Julius Center for Health Sciences and Primary Care; University Medical Center Utrecht; Utrecht The Netherlands
4. Department of Epidemiology; University of Groningen, University Medical Center Groningen; Groningen The Netherlands
5. Institute of Social and Preventive Medicine; University of Bern; Bern Switzerland
6. CTU Bern, Department of Clinical Research; University of Bern; Bern Switzerland
7. F. Hoffmann-La Roche AG; Basel Switzerland